Abstract: A method in a television broadcasting system in which a transmission unit controls the presentation of items of enhanced content during a running program and the presentation of the items of enhanced content is triggered in response to receipt by the transmission unit of periodic indications embedded in the running program, the method comprising: measuring for each periodic indication, a criterion indicative of the quality of that periodic indication; storing the measured criteria as quality data; and, during the running program, if no indication is received by the transmission unit for a predetermined time, accessing the quality date to determine an expected indication quality, and: if the expected indication quality is above a threshold quality level, suspending the triggering of enhanced content, and if the expected indication quality is below the threshold triggering the presentation of enhanced content